<meta charset="UTF-8">
<style>
    .box{
        text-align: center;
    }
    #aset{
        position: fixed;
        left: 50px;
        top: 60px;
    }
    #closebtn{
        position: absolute;
        left: 104px;
        top:0px;
    }
</style>
<div class="box"><img src="images/contentpic.jpg"/></div>
<div id="aset">
    <img src = "images/advpic.jpg"/>
    <img src = "images/close.jpg" id="closebtn"/>
</div>
<script>
    closebtn.onclick = function(){
        aset.style.display = "none";
    }
</script>